Sounds like a good mix for you and your group. I would definitely think about the "loud, look at me" person and give that some thought. All the more reason to have a structured, yet flexible meeting each time. What about announcing at the beginning of each meeting that you are all on a time limit and so it is imperative that you each get a turn to speak, keep to the agenda, and if you give the signal (holding up a wristwatch, or something) then that person needs to close what their saying so you can move on. Just a thought. I would nip that in the bud.

I also think that time will take care of the overflow. There are so many people who attach this romantic idea to being a writer but once they find out how much work it really is, they go, "Ah...I didn't sign up for all of this!" and they bow out...so I would bet your group dwindles a little...enough to make it comfortable for you.

Good job, Louisa!